1. Field of the Invention
This invention relates to improvements in well drilling operations and more particularly, but not by way of limitation, to disc-brake means for protection of the drawworks in a reverse torque situation.
2. Description of the Prior Art
In a well bore drilling operation, such as an oil and/or gas well bore drilling operation, the well bore is usually drilled into the earth by means of a drill bit carried at the lower end of a string of drill pipe. A rotating device known as a rotary table is normally utilized for rotation of the drill pipe during the well bore drilling operation for transmitting rotation to the drill bit, and the power equipment utilized for rotating the rotary table is called a drawworks. The drawworks usually includes a countershaft interposed between a cable drum and the rotary table during the drilling operation and also has a clutch member operable by the countershaft for controlling the driving rotation of the rotary table. As the drill pipe is rotated within the well bore for the drilling operation, a considerable torque builds up in the drill string, particularly in deep well bores, such as twenty-five thousand feet or more in depth, which are being drilled today. When the pipe "hangs up" in the bore for any reason, the backlash or reverse torque applied to the rotary table is exceedingly great. This reverse torque usually completely "tears up" the clutch and may often do great damage to other portions of the drawworks and well drilling equipment, in addition to which some of the drill pipe may be lost in the well bore.